Oscillatory Transpiration and Water Uptake of Avena Plants IV. Transpiratory Response to Sine Shaped Light Cycles

The transpiration rate of individual 6-day-old oat plants was forced to oscillate by cyclic sine-shaped changes in the leaf irradiance (frequency 2 cycles h^?1, amplitude and average value 1.4 mW cm^?2, red light 620–800 nm). By means of a specially designed cuvette with three chambers the transpiration rate from three different segments of the leaf could be measured simultaneously. The leaf segments were illuminated individually and the illumination on each leaf segment could be modulated independently. The experiments showed that there was a strong correlation between the transpiration rates from the different leaf segments, dependent on a coupling mechanism in the plant. The coupling phenomenon disappeared when the root system was eliminated or when the water potential of the root medium was lowered. It was experimentally shown that CO₂ diffusion in the leaf could not be the primary cause for the coupling. Therefore the stomatal dependence on the leaf water potential was considered the most probable reason for the coupling. The frequency of the forcing light cycles could be linearly changed during an experiment and this swept-frequency technique was used to obtain a frequency response of one single oat plant. The technique made it also possible to study the strength of the coupling between different leaf segments.     

Contribution of molecular cladistics to the taxonomy of Rutaceae in China*

The treatment of Rutaceae in the Chinese flora chose to follow Engler in recognizing Rutoideae and Toddalioideae as two separate subfamilies. Morphological and chemical comparisons, however, suggested grouping those two subfamilies in one subfamily, Rutoideae. This move has received support from molecular phylogenetic analyses, which also showed that the Chinese taxa in Euodia should be placed in Tetradium and Melicope following Hartley. Investigations into the chemistry and molecular phylogeny of Murraya also indicated that the species in the section Bergera without yuehchukene should be removed from Murraya. These findings clearly show the value of molecular cladistics to the taxonomy of Rutaceae in China and also directions for further investigations.     

No evidence for optimal fitness at intermediate levels of inbreeding in Drosophila melanogaster

Optimal outbreeding theory predicts fitness benefits to intermediate levels of inbreeding. In the present study, we test for linear (consistent with inbreeding depression) and nonlinear (consistent with optimal outbreeding) effects of inbreeding on reproductive fitness in male and female Drosophila melanogaster . We found linear declines in fitness associated with increased inbreeding for egg-to-adult viability, but not the number of eggs laid or sperm competitive ability. Egg-to-adult viability was also lower in the progeny of inbred males and females mated to unrelated individuals. However, there was no evidence for optimal fitness at intermediate levels of inbreeding for any trait. The present study highlights the importance of considering biologically realistic levels of inbreeding and cross-generational effects when investigating the costs and benefits of mating with relatives.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 98 , 501–510.